Electrical safety demands we know the correct answer to one question: Is there voltage? Since a wrong answer can have life threatening consequences, like arc flash, for example—many companies spend time and money making sure they can answer that question with unerring certainty. When the NFPA published their Standard for Electrical Safety in the Workplace in the year 2000, that document generated essential changes in the way both electrical and mechanical maintenance is performed in today's industrial and commercial facilities. There is no doubt these changes are positive because injuries and deaths caused by electrical accidents have been significantly reduced. Yet, as with any new regulation, employee productivity has been adversely affected because of the Standard.
What is needed is a method and system which would allow for maintaining the reduction in injuries and deaths attributable to NFPA 70e, but in a manner which allows for returning to the level of productivity experienced prior to NFPA 70e.
Non-contact voltage detectors (NCVD's) are one example of devices which may be used to determine whether or not voltage is present at a location (such as a wire or contact point) being probed. But, because of the possibility of false negatives, meaning that the voltage tester falsely indicates that there is not a voltage when there actually is, NCVD's have not been considered a reliable means in determining electrical isolation. Because of the possibility of a false negative reading, some plants will not allow maintenance workers to carry them. Because a NCVD relies on capacitance, external factors not related to the tested conductor may affect the voltage reading which creates a potential false negative situation when voltage is present. Examples of factors that affect the operation of a NCVD include, without limitation, AC Only, minimum voltage level, phase cancellation, metal barriers (small enclosures), underground cables, hand position, temperature, induced voltage, and frequency. Despite these problems, a voltage portal correctly installed into an electrical panel increases the reliability of the NCVD voltage reading by reducing these variables. In addition, because NVCDs are portable, they can also be checked to an independent voltage source as per NFPA 70E 120.1(5).
Another way to test for voltages is to use a voltage indicator. Voltage indicators installed by qualified electricians are hardwired to the main power disconnect and earth ground. Installation is simple because a phase-neutral high impedance voltage detection circuit on each phase senses and illuminates AC/DC voltage. Two issues with voltage indicators are that (1) it is impractical to verify the voltage indicator to another independent voltage source as attempting to do so adds complexity and reduces reliability and (2) since the voltage indicator's sole purpose is to indicate voltage, any electrical connection between the source voltage and the voltage indicator increases the chance of a false negative voltage reading.
Therefore, what is also needed is an improved device and system for electrical safety.